It seems appropriate that one of the best shows of 2018 should be back for more before the year’s even over, as Starz’s Counterpart often has us seeing double.

A Berlin-set spy drama that takes place in parallel worlds, Counterpart, whose second season premieres on Sunday, Dec. 9, boasts dual roles not only for its lead, Oscar-winning actor J.K. Simmons, but for other cast members, including Olivia Williams, who should be busier than ever now that one of her two characters has emerged from a coma.

Over the course of the first season, I came to appreciate Justin Marks' story of a secret conflict between have and have-not societies. But the initial attraction of Counterpart was the opportunity to see Simmons in not one, but two leading roles. A veteran character actor, he was probably best known, before those Farmers Insurance commercials came along, for playing a neo-Nazi on HBO’s prison drama Oz. A 2015 Academy Award for portraying the tyrannical music teacher in Whiplash affected his career “significantly,” Simmons told me in an interview last January.

His roles in Counterpart, in which he plays Howard Silk, a mild-mannered but long-frustrated bureaucrat whose life is changed when he meets his far more aggressive — and successful — opposite number from a harsher world, were an opportunity to showcase more of his range.

Although it’s the differences between the two Howards that he first noticed, Simmons said he eventually became more interested in “finding the places where they intersect.”

And it’s that story, of each of the Howards discovering parts of himself that may have lain dormant, that continues to have the most resonance in the new season, as one Howard lives with the other’s no longer comatose wife, Emily (Williams), while a world away, Emily’s actual husband is held captive, and the other Emily, long divorced from “her” Howard, tackles a new assignment.

Simmons and Williams aren’t alone, of course, in pulling double duty. TV has a long history of employing one actor to play soap-opera evil (or long-lost) twins — or, in the case of The Patty Duke Show, “identical cousins” — and it’s continued to find opportunities for actors eager to play opposite themselves, among them:

James Franco. Roles: Vincent and Frankie Martino in HBO’s The Deuce. Relationship: Identical twins, characters inspired by real-life twin brothers whom creators David Simon and George Pelecanos learned of while researching the drama about the 1970s porn industry. How to tell them apart: Frankie slicks his hair back. Twice as nice? Not really. Vincent’s story is the more interesting, but a little Franco goes a long way, and Maggie Gyllenhaal’s performance as hooker-turned-director Eileen “Candy” Merrell is the more memorable.

Vanessa Hudgens. Roles: Stacy De Novo, a baker from Chicago, and Lady Margaret Delacourt, duchess of fictional Montenaro, in Netflix’s holiday movie The Princess Switch. Relationship: Possibly distant cousins, but that’s as far anyone gets in explaining why they look enough alike to be able to exchange places, a few days before Stacy’s to compete in an international baking contest and Margaret’s supposed to marry the prince of Belgravia (Sam Palladio, Nashville). How to tell them apart: Once they cut Stacy’s hair, and Stacy starts talking with Margaret’s British accent, it’s hard. But since Margaret seems to have learned her American English from old TV shows, it’s not impossible. (If you’re actually paying attention by this point.) Twice as nice? Let’s just say that unlike Netflix’s painfully bad A Christmas Prince: The Royal Wedding, The Princess Switch, thanks to Hudgens' energetic performances as Stacy, Margaret, Stacy-playing-Margaret, and Margaret-playing-Stacy, is kind of fun. Even if it makes no sense whatsoever.

Tatiana Maslany. Roles: Five main characters and several other minor ones in BBC America’s Orphan Black, which ended last year but which can be seen on Amazon Prime Video. Relationship: Clones. How to tell them apart: Without much difficulty, since Maslany, with considerable help from hair and makeup, portrayed each differently. Twice (or multiple times) as nice? The actress won a much-deserved Emmy in 2016 for performances that could have felt like an acting exercise but somehow never did.

Ewan McGregor. Roles: Emmit and Ray Stussy in the most recent season of FX’s Fargo. Relationship: Brothers. How to tell them apart: Emmit, who’s two years older, looks fit and prosperous, and has a full head of hair, thanks to McGregor’s curly wig. Ray’s balding and has a paunch. Twice as nice? You betcha!

Zach Galifianakis. Roles: Chip and Dale Baskets (yes, like the Walt Disney chipmunks) in FX’s Baskets. Relationship: Twin brothers, one who began the series three seasons ago as a particularly sad clown, the other who’s been more conventionally successful but whose life also seems kind of sad. (Did I mention this is a comedy?) How to tell them apart: They both look an awful lot like Galifianakis, but Dale appears to own a comb. Twice as nice? The actor scored an Emmy nomination for his dual roles in 2017. But both his characters are overshadowed by Louie Anderson, who’s channeled his own late mother to play the Baskets family matriarch, Christine, and who’s been nominated as a supporting actor in each of the show’s three seasons, winning in 2016.

Yael Grobglas. Roles: Petra Solano and Anezka (who at one point pretended to be Petra) in the CW’s Jane the Virgin. Relationship: Twin sisters. How to tell them apart: Anezka, Petra’s long-lost sister, was a brunette who spoke with a Czech accent. Twice as nice? The absurdity of the twins' story was perfectly in keeping with the show’s telenovela roots, and Grobglas got to show off more of her comic chops. With Anezka now dead — at least as dependably as anyone can be said to be dead on Jane the Virgin — she’s back to just Petra as the show returns for its fifth and final season in 2019.

Tobias Menzies. Roles: In earlier seasons of Starz’s Outlander, he played both Frank Randall, a professor who was married to the time-traveling heroine Claire (Caitriona Balfe) in the 20th century, as well as his own 18th-century ancestor, a sadistic British officer known as “Black Jack” Randall who menaced Claire and her 18th-century husband, Jamie (Sam Heughan). How to tell them apart: The red coat is one tip-off you’re seeing Black Jack. Twice as nice? Neither character is warm and fuzzy (though Frank, at least, has his reasons), but Menzies is terrific. Look for him in the next season of Netflix’s The Crown, where he’ll be taking over the role of Britain’s Prince Philip from Matt Smith.

Counterpart. 9 p.m. Sunday, Dec. 9, Starz.